1. Field of the Invention
The invention relates to the field electrical discrete devices and in particular to flat transformers formed in slabs of ferrite material.
2. Description of the Prior Art
A classical transformer is comprised of a magnetic core of any one of a large variety of shapes around which is wound two or more coils. One of the coils is used as an input coil and is defined as the primary winding. The other coil is used as an output coil and is defined as the secondary winding. There may be in fact any combination of multiple input and output windings as desired in the application. Since the windings are wrapped around the same magnetic core, whatever its shape may be, the effective areas of cross section of the windings are approximately the same. Therefore, the voltage transformation which is achieved by the primary and secondary windings depends upon the ratio of their turns.
A number of problems arise in the situation of high frequency power applications. Typically the number of turns in the primary or secondary windings is such that high resistive losses are encountered. Although these losses can usually be accepted in low power low frequency applications, at higher frequency applications the physics of electrical conduction in the windings is qualitatively different in that skin effects and proximity effects preclude the efficient use of the total wire cross section. The resistive losses thus become exaggerated at high frequencies.
Moreover, because of the multiple number of turns in each of the windings on the transformer, it is difficult to manufacture a low profile or flat power transformer. The ability to manufacture a flat power transformer is particularly accentuated where multiple output coils are required on the transformer.
The prior art has devised a number of designs wherein multiple slabs of ferromagnetic material are utilized as the core structure for a transformer. Examples can be seen in HASE, "Regulating Transformer with Magnetic Shunt", U.S. Pat. No. 4,206,434 (1980); KOUYOUMJIAN, "Electric Control Apparatus", U.S. Pat. No. 1,910,172 (1933); STIMLER, "Alternating Electric Current Transformer", U.S. Pat. No. 2,598,617 (1952); and DOWLING, "Electrical Translating Apparatus", U.S. Pat. No. 1,793,312 (1931).
Although many of such prior art devices such as KOUYOUMJIAN and HASE may have aspect ratios which make them wider and taller than they are thick, they are not in reality extremely thin or flat transformers. Furthermore, the electrical transforming function which has been performed by each of these devices still depends upon the ratio of turns of the primary and secondary coils, and is thus subject to each of the high frequency defects discussed above.
Therefore, what is needed is a design for an electrical transformer which allows the transformer to be both extremely slim or flat and which can be utilized in high frequency applications without suffering the defects of prior art transformers.